Hydraulic fracturing (also called hydrofracturing, hydrofracking, fracking or fraccing) is a well-stimulation technique in which rock is fractured by a pressurized liquid. The process involves the high-pressure injection of fracking fluid (such as water containing proppants suspended with the aid of thickening agents) into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely. When the hydraulic pressure is removed from the well, proppants hold the fractures open.
Proppants are solid materials in the form of small grains, such as sand or ceramic particulates, that are introduced into fracking formations in order to prevent small fractures in the earth from collapsing during or following a fracturing treatment. Proppants are often delivered to fractures using carrier fluids. Higher viscosity carrier fluids carry proppants more effectively, but that viscosity also creates friction pressure within the pumps that pump the carrier fluid into the formation.
Guar is a botanically sourced substance that is commonly used as a thickening agent in proppant carrier fluids. Also called guaran or guar gum, guar is a galactomannan made from the ground endosperm of guar beans. Crosslinking hydrated guar suspensions, or suspensions of various guar derivatives, can create a gel fluid with relatively high viscosity. Higher viscosity fluids can carry higher concentrations of proppant, thereby enhancing the proppant delivery effectiveness of the system and enabling increased fracture width. Higher viscosity fluids also result in reduced fluid loss, which assists in increasing fracture length.